// Copyright 2015 the V8 project authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#include "src/v8.h"

#if V8_TARGET_ARCH_S390

#include "src/assembler-inl.h"
#include "src/base/bits.h"
#include "src/log.h"
#include "src/macro-assembler.h"
#include "src/regexp/regexp-macro-assembler.h"
#include "src/regexp/regexp-stack.h"
#include "src/snapshot/embedded-data.h"
#include "src/regexp/s390/regexp-macro-assembler-s390.h"
#include "src/unicode.h"

namespace v8 {
namespace internal {

    /*
 * This assembler uses the following register assignment convention
 * - r6: Temporarily stores the index of capture start after a matching pass
 *        for a global regexp.
 * - r7: Pointer to current Code object including heap object tag.
 * - r8: Current position in input, as negative offset from end of string.
 *        Please notice that this is the byte offset, not the character offset!
 * - r9: Currently loaded character. Must be loaded using
 *        LoadCurrentCharacter before using any of the dispatch methods.
 * - r13: Points to tip of backtrack stack
 * - r10: End of input (points to byte after last character in input).
 * - r11: Frame pointer. Used to access arguments, local variables and
 *         RegExp registers.
 * - r12: IP register, used by assembler. Very volatile.
 * - r15/sp : Points to tip of C stack.
 *
 * The remaining registers are free for computations.
 * Each call to a public method should retain this convention.
 *
 * The stack will have the following structure:
 *  - fp[108] Isolate* isolate   (address of the current isolate)
 *  - fp[104] direct_call        (if 1, direct call from JavaScript code,
 *                                if 0, call through the runtime system).
 *  - fp[100] stack_area_base    (high end of the memory area to use as
 *                                backtracking stack).
 *  - fp[96]  capture array size (may fit multiple sets of matches)
 *  - fp[0..96] zLinux ABI register saving area
 *  --- sp when called ---
 *  --- frame pointer ----
 *  - fp[-4]  direct_call        (if 1, direct call from JavaScript code,
 *                                if 0, call through the runtime system).
 *  - fp[-8]  stack_area_base    (high end of the memory area to use as
 *                                backtracking stack).
 *  - fp[-12] capture array size (may fit multiple sets of matches)
 *  - fp[-16] int* capture_array (int[num_saved_registers_], for output).
 *  - fp[-20] end of input       (address of end of string).
 *  - fp[-24] start of input     (address of first character in string).
 *  - fp[-28] start index        (character index of start).
 *  - fp[-32] void* input_string (location of a handle containing the string).
 *  - fp[-36] success counter    (only for global regexps to count matches).
 *  - fp[-40] Offset of location before start of input (effectively character
 *            string start - 1). Used to initialize capture registers to a
 *            non-position.
 *  - fp[-44] At start (if 1, we are starting at the start of the
 *    string, otherwise 0)
 *  - fp[-48] register 0         (Only positions must be stored in the first
 *  -         register 1          num_saved_registers_ registers)
 *  -         ...
 *  -         register num_registers-1
 *  --- sp ---
 *
 * The first num_saved_registers_ registers are initialized to point to
 * "character -1" in the string (i.e., char_size() bytes before the first
 * character of the string). The remaining registers start out as garbage.
 *
 * The data up to the return address must be placed there by the calling
 * code and the remaining arguments are passed in registers, e.g. by calling the
 * code entry as cast to a function with the signature:
 * int (*match)(String input_string,
 *              int start_index,
 *              Address start,
 *              Address end,
 *              int* capture_output_array,
 *              int num_capture_registers,
 *              byte* stack_area_base,
 *              bool direct_call = false,
 *              Isolate* isolate);
 * The call is performed by NativeRegExpMacroAssembler::Execute()
 * (in regexp-macro-assembler.cc) via the GeneratedCode wrapper.
 */

#define __ ACCESS_MASM(masm_)

    const int RegExpMacroAssemblerS390::kRegExpCodeSize;

    RegExpMacroAssemblerS390::RegExpMacroAssemblerS390(Isolate* isolate, Zone* zone,
        Mode mode,
        int registers_to_save)
        : NativeRegExpMacroAssembler(isolate, zone)
        , masm_(new MacroAssembler(isolate, CodeObjectRequired::kYes,
              NewAssemblerBuffer(kRegExpCodeSize)))
        , mode_(mode)
        , num_registers_(registers_to_save)
        , num_saved_registers_(registers_to_save)
        , entry_label_()
        , start_label_()
        , success_label_()
        , backtrack_label_()
        , exit_label_()
        , internal_failure_label_()
    {
        DCHECK_EQ(0, registers_to_save % 2);

        __ b(&entry_label_); // We'll write the entry code later.
        // If the code gets too big or corrupted, an internal exception will be
        // raised, and we will exit right away.
        __ bind(&internal_failure_label_);
        __ LoadImmP(r2, Operand(FAILURE));
        __ Ret();
        __ bind(&start_label_); // And then continue from here.
    }

    RegExpMacroAssemblerS390::~RegExpMacroAssemblerS390()
    {
        delete masm_;
        // Unuse labels in case we throw away the assembler without calling GetCode.
        entry_label_.Unuse();
        start_label_.Unuse();
        success_label_.Unuse();
        backtrack_label_.Unuse();
        exit_label_.Unuse();
        check_preempt_label_.Unuse();
        stack_overflow_label_.Unuse();
        internal_failure_label_.Unuse();
    }

    int RegExpMacroAssemblerS390::stack_limit_slack()
    {
        return RegExpStack::kStackLimitSlack;
    }

    void RegExpMacroAssemblerS390::AdvanceCurrentPosition(int by)
    {
        if (by != 0) {
            __ AddP(current_input_offset(), Operand(by * char_size()));
        }
    }

    void RegExpMacroAssemblerS390::AdvanceRegister(int reg, int by)
    {
        DCHECK_LE(0, reg);
        DCHECK_GT(num_registers_, reg);
        if (by != 0) {
            if (CpuFeatures::IsSupported(GENERAL_INSTR_EXT) && is_int8(by)) {
                __ AddMI(register_location(reg), Operand(by));
            } else {
                __ LoadP(r2, register_location(reg), r0);
                __ mov(r0, Operand(by));
                __ AddRR(r2, r0);
                __ StoreP(r2, register_location(reg));
            }
        }
    }

    void RegExpMacroAssemblerS390::Backtrack()
    {
        CheckPreemption();
        // Pop Code offset from backtrack stack, add Code and jump to location.
        Pop(r2);
        __ AddP(r2, code_pointer());
        __ b(r2);
    }

    void RegExpMacroAssemblerS390::Bind(Label* label) { __ bind(label); }

    void RegExpMacroAssemblerS390::CheckCharacter(uint32_t c, Label* on_equal)
    {
        __ CmpLogicalP(current_character(), Operand(c));
        BranchOrBacktrack(eq, on_equal);
    }

    void RegExpMacroAssemblerS390::CheckCharacterGT(uc16 limit, Label* on_greater)
    {
        __ CmpLogicalP(current_character(), Operand(limit));
        BranchOrBacktrack(gt, on_greater);
    }

    void RegExpMacroAssemblerS390::CheckAtStart(Label* on_at_start)
    {
        __ LoadP(r3, MemOperand(frame_pointer(), kStringStartMinusOne));
        __ AddP(r2, current_input_offset(), Operand(-char_size()));
        __ CmpP(r2, r3);
        BranchOrBacktrack(eq, on_at_start);
    }

    void RegExpMacroAssemblerS390::CheckNotAtStart(int cp_offset,
        Label* on_not_at_start)
    {
        __ LoadP(r3, MemOperand(frame_pointer(), kStringStartMinusOne));
        __ AddP(r2, current_input_offset(),
            Operand(-char_size() + cp_offset * char_size()));
        __ CmpP(r2, r3);
        BranchOrBacktrack(ne, on_not_at_start);
    }

    void RegExpMacroAssemblerS390::CheckCharacterLT(uc16 limit, Label* on_less)
    {
        __ CmpLogicalP(current_character(), Operand(limit));
        BranchOrBacktrack(lt, on_less);
    }

    void RegExpMacroAssemblerS390::CheckGreedyLoop(Label* on_equal)
    {
        Label backtrack_non_equal;
        __ CmpP(current_input_offset(), MemOperand(backtrack_stackpointer(), 0));
        __ bne(&backtrack_non_equal);
        __ AddP(backtrack_stackpointer(), Operand(kPointerSize));

        BranchOrBacktrack(al, on_equal);
        __ bind(&backtrack_non_equal);
    }

    void RegExpMacroAssemblerS390::CheckNotBackReferenceIgnoreCase(
        int start_reg, bool read_backward, bool unicode, Label* on_no_match)
    {
        Label fallthrough;
        __ LoadP(r2, register_location(start_reg)); // Index of start of
            // capture
        __ LoadP(r3, register_location(start_reg + 1)); // Index of end
        __ SubP(r3, r3, r2);

        // At this point, the capture registers are either both set or both cleared.
        // If the capture length is zero, then the capture is either empty or cleared.
        // Fall through in both cases.
        __ beq(&fallthrough);

        // Check that there are enough characters left in the input.
        if (read_backward) {
            __ LoadP(r5, MemOperand(frame_pointer(), kStringStartMinusOne));
            __ AddP(r5, r5, r3);
            __ CmpP(current_input_offset(), r5);
            BranchOrBacktrack(le, on_no_match);
        } else {
            __ AddP(r0, r3, current_input_offset());
            BranchOrBacktrack(gt, on_no_match);
        }

        if (mode_ == LATIN1) {
            Label success;
            Label fail;
            Label loop_check;

            // r2 - offset of start of capture
            // r3 - length of capture
            __ AddP(r2, end_of_input_address());
            __ AddP(r4, current_input_offset(), end_of_input_address());
            if (read_backward) {
                __ SubP(r4, r4, r3); // Offset by length when matching backwards.
            }
            __ mov(r1, Operand::Zero());

            // r1 - Loop index
            // r2 - Address of start of capture.
            // r4 - Address of current input position.

            Label loop;
            __ bind(&loop);
            __ LoadlB(r5, MemOperand(r2, r1));
            __ LoadlB(r6, MemOperand(r4, r1));

            __ CmpP(r6, r5);
            __ beq(&loop_check);

            // Mismatch, try case-insensitive match (converting letters to lower-case).
            __ Or(r5, Operand(0x20)); // Convert capture character to lower-case.
            __ Or(r6, Operand(0x20)); // Also convert input character.
            __ CmpP(r6, r5);
            __ bne(&fail);
            __ SubP(r5, Operand('a'));
            __ CmpLogicalP(r5, Operand('z' - 'a')); // Is r5 a lowercase letter?
            __ ble(&loop_check); // In range 'a'-'z'.
            // Latin-1: Check for values in range [224,254] but not 247.
            __ SubP(r5, Operand(224 - 'a'));
            __ CmpLogicalP(r5, Operand(254 - 224));
            __ bgt(&fail); // Weren't Latin-1 letters.
            __ CmpLogicalP(r5, Operand(247 - 224)); // Check for 247.
            __ beq(&fail);

            __ bind(&loop_check);
            __ la(r1, MemOperand(r1, char_size()));
            __ CmpP(r1, r3);
            __ blt(&loop);
            __ b(&success);

            __ bind(&fail);
            BranchOrBacktrack(al, on_no_match);

            __ bind(&success);
            // Compute new value of character position after the matched part.
            __ SubP(current_input_offset(), r4, end_of_input_address());
            if (read_backward) {
                __ LoadP(r2, register_location(start_reg)); // Index of start of capture
                __ LoadP(r3,
                    register_location(start_reg + 1)); // Index of end of capture
                __ AddP(current_input_offset(), current_input_offset(), r2);
                __ SubP(current_input_offset(), current_input_offset(), r3);
            }
            __ AddP(current_input_offset(), r1);
        } else {
            DCHECK(mode_ == UC16);
            int argument_count = 4;
            __ PrepareCallCFunction(argument_count, r4);

            // r2 - offset of start of capture
            // r3 - length of capture

            // Put arguments into arguments registers.
            // Parameters are
            //   r2: Address byte_offset1 - Address captured substring's start.
            //   r3: Address byte_offset2 - Address of current character position.
            //   r4: size_t byte_length - length of capture in bytes(!)
            //   r5: Isolate* isolate or 0 if unicode flag.

            // Address of start of capture.
            __ AddP(r2, end_of_input_address());
            // Length of capture.
            __ LoadRR(r4, r3);
            // Save length in callee-save register for use on return.
            __ LoadRR(r6, r3);
            // Address of current input position.
            __ AddP(r3, current_input_offset(), end_of_input_address());
            if (read_backward) {
                __ SubP(r3, r3, r6);
            }
// Isolate.
#ifdef V8_INTL_SUPPORT
            if (unicode) {
                __ LoadImmP(r5, Operand::Zero());
            } else // NOLINT
#endif // V8_INTL_SUPPORT
            {
                __ mov(r5, Operand(ExternalReference::isolate_address(isolate())));
            }

            {
                AllowExternalCallThatCantCauseGC scope(masm_);
                ExternalReference function = ExternalReference::re_case_insensitive_compare_uc16(isolate());
                __ CallCFunction(function, argument_count);
            }

            // Check if function returned non-zero for success or zero for failure.
            __ CmpP(r2, Operand::Zero());
            BranchOrBacktrack(eq, on_no_match);

            // On success, advance position by length of capture.
            if (read_backward) {
                __ SubP(current_input_offset(), current_input_offset(), r6);
            } else {
                __ AddP(current_input_offset(), current_input_offset(), r6);
            }
        }

        __ bind(&fallthrough);
    }

    void RegExpMacroAssemblerS390::CheckNotBackReference(int start_reg,
        bool read_backward,
        Label* on_no_match)
    {
        Label fallthrough;

        // Find length of back-referenced capture.
        __ LoadP(r2, register_location(start_reg));
        __ LoadP(r3, register_location(start_reg + 1));
        __ SubP(r3, r3, r2); // Length to check.

        // At this point, the capture registers are either both set or both cleared.
        // If the capture length is zero, then the capture is either empty or cleared.
        // Fall through in both cases.
        __ beq(&fallthrough);

        // Check that there are enough characters left in the input.
        if (read_backward) {
            __ LoadP(r5, MemOperand(frame_pointer(), kStringStartMinusOne));
            __ AddP(r5, r5, r3);
            __ CmpP(current_input_offset(), r5);
            BranchOrBacktrack(le, on_no_match);
        } else {
            __ AddP(r0, r3, current_input_offset());
            BranchOrBacktrack(gt, on_no_match, cr0);
        }

        // r2 - offset of start of capture
        // r3 - length of capture
        __ la(r2, MemOperand(r2, end_of_input_address()));
        __ la(r4, MemOperand(current_input_offset(), end_of_input_address()));
        if (read_backward) {
            __ SubP(r4, r4, r3); // Offset by length when matching backwards.
        }
        __ mov(r1, Operand::Zero());

        Label loop;
        __ bind(&loop);
        if (mode_ == LATIN1) {
            __ LoadlB(r5, MemOperand(r2, r1));
            __ LoadlB(r6, MemOperand(r4, r1));
        } else {
            DCHECK(mode_ == UC16);
            __ LoadLogicalHalfWordP(r5, MemOperand(r2, r1));
            __ LoadLogicalHalfWordP(r6, MemOperand(r4, r1));
        }
        __ la(r1, MemOperand(r1, char_size()));
        __ CmpP(r5, r6);
        BranchOrBacktrack(ne, on_no_match);
        __ CmpP(r1, r3);
        __ blt(&loop);

        // Move current character position to position after match.
        __ SubP(current_input_offset(), r4, end_of_input_address());
        if (read_backward) {
            __ LoadP(r2, register_location(start_reg)); // Index of start of capture
            __ LoadP(r3, register_location(start_reg + 1)); // Index of end of capture
            __ AddP(current_input_offset(), current_input_offset(), r2);
            __ SubP(current_input_offset(), current_input_offset(), r3);
        }
        __ AddP(current_input_offset(), r1);

        __ bind(&fallthrough);
    }

    void RegExpMacroAssemblerS390::CheckNotCharacter(unsigned c,
        Label* on_not_equal)
    {
        __ CmpLogicalP(current_character(), Operand(c));
        BranchOrBacktrack(ne, on_not_equal);
    }

    void RegExpMacroAssemblerS390::CheckCharacterAfterAnd(uint32_t c, uint32_t mask,
        Label* on_equal)
    {
        __ AndP(r2, current_character(), Operand(mask));
        if (c != 0) {
            __ CmpLogicalP(r2, Operand(c));
        }
        BranchOrBacktrack(eq, on_equal);
    }

    void RegExpMacroAssemblerS390::CheckNotCharacterAfterAnd(unsigned c,
        unsigned mask,
        Label* on_not_equal)
    {
        __ AndP(r2, current_character(), Operand(mask));
        if (c != 0) {
            __ CmpLogicalP(r2, Operand(c));
        }
        BranchOrBacktrack(ne, on_not_equal);
    }

    void RegExpMacroAssemblerS390::CheckNotCharacterAfterMinusAnd(
        uc16 c, uc16 minus, uc16 mask, Label* on_not_equal)
    {
        DCHECK_GT(String::kMaxUtf16CodeUnit, minus);
        __ lay(r2, MemOperand(current_character(), -minus));
        __ And(r2, Operand(mask));
        if (c != 0) {
            __ CmpLogicalP(r2, Operand(c));
        }
        BranchOrBacktrack(ne, on_not_equal);
    }

    void RegExpMacroAssemblerS390::CheckCharacterInRange(uc16 from, uc16 to,
        Label* on_in_range)
    {
        __ lay(r2, MemOperand(current_character(), -from));
        __ CmpLogicalP(r2, Operand(to - from));
        BranchOrBacktrack(le, on_in_range); // Unsigned lower-or-same condition.
    }

    void RegExpMacroAssemblerS390::CheckCharacterNotInRange(
        uc16 from, uc16 to, Label* on_not_in_range)
    {
        __ lay(r2, MemOperand(current_character(), -from));
        __ CmpLogicalP(r2, Operand(to - from));
        BranchOrBacktrack(gt, on_not_in_range); // Unsigned higher condition.
    }

    void RegExpMacroAssemblerS390::CheckBitInTable(Handle<ByteArray> table,
        Label* on_bit_set)
    {
        __ mov(r2, Operand(table));
        Register index = current_character();
        if (mode_ != LATIN1 || kTableMask != String::kMaxOneByteCharCode) {
            __ AndP(r3, current_character(), Operand(kTableSize - 1));
            index = r3;
        }
        __ LoadlB(r2,
            MemOperand(r2, index, (ByteArray::kHeaderSize - kHeapObjectTag)));
        __ CmpP(r2, Operand::Zero());
        BranchOrBacktrack(ne, on_bit_set);
    }

    bool RegExpMacroAssemblerS390::CheckSpecialCharacterClass(uc16 type,
        Label* on_no_match)
    {
        // Range checks (c in min..max) are generally implemented by an unsigned
        // (c - min) <= (max - min) check
        switch (type) {
        case 's':
            // Match space-characters
            if (mode_ == LATIN1) {
                // One byte space characters are '\t'..'\r', ' ' and \u00a0.
                Label success;
                __ CmpP(current_character(), Operand(' '));
                __ beq(&success);
                // Check range 0x09..0x0D
                __ SubP(r2, current_character(), Operand('\t'));
                __ CmpLogicalP(r2, Operand('\r' - '\t'));
                __ ble(&success);
                // \u00a0 (NBSP).
                __ CmpLogicalP(r2, Operand(0x00A0 - '\t'));
                BranchOrBacktrack(ne, on_no_match);
                __ bind(&success);
                return true;
            }
            return false;
        case 'S':
            // The emitted code for generic character classes is good enough.
            return false;
        case 'd':
            // Match ASCII digits ('0'..'9')
            __ SubP(r2, current_character(), Operand('0'));
            __ CmpLogicalP(r2, Operand('9' - '0'));
            BranchOrBacktrack(gt, on_no_match);
            return true;
        case 'D':
            // Match non ASCII-digits
            __ SubP(r2, current_character(), Operand('0'));
            __ CmpLogicalP(r2, Operand('9' - '0'));
            BranchOrBacktrack(le, on_no_match);
            return true;
        case '.': {
            // Match non-newlines (not 0x0A('\n'), 0x0D('\r'), 0x2028 and 0x2029)
            __ XorP(r2, current_character(), Operand(0x01));
            // See if current character is '\n'^1 or '\r'^1, i.e., 0x0B or 0x0C
            __ SubP(r2, Operand(0x0B));
            __ CmpLogicalP(r2, Operand(0x0C - 0x0B));
            BranchOrBacktrack(le, on_no_match);
            if (mode_ == UC16) {
                // Compare original value to 0x2028 and 0x2029, using the already
                // computed (current_char ^ 0x01 - 0x0B). I.e., check for
                // 0x201D (0x2028 - 0x0B) or 0x201E.
                __ SubP(r2, Operand(0x2028 - 0x0B));
                __ CmpLogicalP(r2, Operand(1));
                BranchOrBacktrack(le, on_no_match);
            }
            return true;
        }
        case 'n': {
            // Match newlines (0x0A('\n'), 0x0D('\r'), 0x2028 and 0x2029)
            __ XorP(r2, current_character(), Operand(0x01));
            // See if current character is '\n'^1 or '\r'^1, i.e., 0x0B or 0x0C
            __ SubP(r2, Operand(0x0B));
            __ CmpLogicalP(r2, Operand(0x0C - 0x0B));
            if (mode_ == LATIN1) {
                BranchOrBacktrack(gt, on_no_match);
            } else {
                Label done;
                __ ble(&done);
                // Compare original value to 0x2028 and 0x2029, using the already
                // computed (current_char ^ 0x01 - 0x0B). I.e., check for
                // 0x201D (0x2028 - 0x0B) or 0x201E.
                __ SubP(r2, Operand(0x2028 - 0x0B));
                __ CmpLogicalP(r2, Operand(1));
                BranchOrBacktrack(gt, on_no_match);
                __ bind(&done);
            }
            return true;
        }
        case 'w': {
            if (mode_ != LATIN1) {
                // Table is 1256 entries, so all LATIN1 characters can be tested.
                __ CmpP(current_character(), Operand('z'));
                BranchOrBacktrack(gt, on_no_match);
            }
            ExternalReference map = ExternalReference::re_word_character_map(isolate());
            __ mov(r2, Operand(map));
            __ LoadlB(r2, MemOperand(r2, current_character()));
            __ CmpLogicalP(r2, Operand::Zero());
            BranchOrBacktrack(eq, on_no_match);
            return true;
        }
        case 'W': {
            Label done;
            if (mode_ != LATIN1) {
                // Table is 256 entries, so all LATIN characters can be tested.
                __ CmpLogicalP(current_character(), Operand('z'));
                __ bgt(&done);
            }
            ExternalReference map = ExternalReference::re_word_character_map(isolate());
            __ mov(r2, Operand(map));
            __ LoadlB(r2, MemOperand(r2, current_character()));
            __ CmpLogicalP(r2, Operand::Zero());
            BranchOrBacktrack(ne, on_no_match);
            if (mode_ != LATIN1) {
                __ bind(&done);
            }
            return true;
        }
        case '*':
            // Match any character.
            return true;
        // No custom implementation (yet): s(UC16), S(UC16).
        default:
            return false;
        }
    }

    void RegExpMacroAssemblerS390::Fail()
    {
        __ LoadImmP(r2, Operand(FAILURE));
        __ b(&exit_label_);
    }

    Handle<HeapObject> RegExpMacroAssemblerS390::GetCode(Handle<String> source)
    {
        Label return_r2;

        // Finalize code - write the entry point code now we know how many
        // registers we need.

        // Entry code:
        __ bind(&entry_label_);

        // Tell the system that we have a stack frame.  Because the type
        // is MANUAL, no is generated.
        FrameScope scope(masm_, StackFrame::MANUAL);

        // Ensure register assigments are consistent with callee save mask
        DCHECK(r6.bit() & kRegExpCalleeSaved);
        DCHECK(code_pointer().bit() & kRegExpCalleeSaved);
        DCHECK(current_input_offset().bit() & kRegExpCalleeSaved);
        DCHECK(current_character().bit() & kRegExpCalleeSaved);
        DCHECK(backtrack_stackpointer().bit() & kRegExpCalleeSaved);
        DCHECK(end_of_input_address().bit() & kRegExpCalleeSaved);
        DCHECK(frame_pointer().bit() & kRegExpCalleeSaved);

        // zLinux ABI
        //    Incoming parameters:
        //          r2: input_string
        //          r3: start_index
        //          r4: start addr
        //          r5: end addr
        //          r6: capture output arrray
        //    Requires us to save the callee-preserved registers r6-r13
        //    General convention is to also save r14 (return addr) and
        //    sp/r15 as well in a single STM/STMG
        __ StoreMultipleP(r6, sp, MemOperand(sp, 6 * kPointerSize));

        // Load stack parameters from caller stack frame
        __ LoadMultipleP(r7, r9,
            MemOperand(sp, kStackFrameExtraParamSlot * kPointerSize));
        // r7 = capture array size
        // r8 = stack area base
        // r9 = direct call

        // Actually emit code to start a new stack frame.
        // Push arguments
        // Save callee-save registers.
        // Start new stack frame.
        // Store link register in existing stack-cell.
        // Order here should correspond to order of offset constants in header file.
        //
        // Set frame pointer in space for it if this is not a direct call
        // from generated code.
        __ LoadRR(frame_pointer(), sp);
        __ lay(sp, MemOperand(sp, -10 * kPointerSize));
        __ mov(r1, Operand::Zero()); // success counter
        __ LoadRR(r0, r1); // offset of location
        __ StoreMultipleP(r0, r9, MemOperand(sp, 0));

        // Check if we have space on the stack for registers.
        Label stack_limit_hit;
        Label stack_ok;

        ExternalReference stack_limit = ExternalReference::address_of_stack_limit(isolate());
        __ mov(r2, Operand(stack_limit));
        __ LoadP(r2, MemOperand(r2));
        __ SubP(r2, sp, r2);
        // Handle it if the stack pointer is already below the stack limit.
        __ ble(&stack_limit_hit);
        // Check if there is room for the variable number of registers above
        // the stack limit.
        __ CmpLogicalP(r2, Operand(num_registers_ * kPointerSize));
        __ bge(&stack_ok);
        // Exit with OutOfMemory exception. There is not enough space on the stack
        // for our working registers.
        __ mov(r2, Operand(EXCEPTION));
        __ b(&return_r2);

        __ bind(&stack_limit_hit);
        CallCheckStackGuardState(r2);
        __ CmpP(r2, Operand::Zero());
        // If returned value is non-zero, we exit with the returned value as result.
        __ bne(&return_r2);

        __ bind(&stack_ok);

        // Allocate space on stack for registers.
        __ lay(sp, MemOperand(sp, (-num_registers_ * kPointerSize)));
        // Load string end.
        __ LoadP(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
        // Load input start.
        __ LoadP(r4, MemOperand(frame_pointer(), kInputStart));
        // Find negative length (offset of start relative to end).
        __ SubP(current_input_offset(), r4, end_of_input_address());
        __ LoadP(r3, MemOperand(frame_pointer(), kStartIndex));
        // Set r1 to address of char before start of the input string
        // (effectively string position -1).
        __ LoadRR(r1, r4);
        __ SubP(r1, current_input_offset(), Operand(char_size()));
        if (mode_ == UC16) {
            __ ShiftLeftP(r0, r3, Operand(1));
            __ SubP(r1, r1, r0);
        } else {
            __ SubP(r1, r1, r3);
        }
        // Store this value in a local variable, for use when clearing
        // position registers.
        __ StoreP(r1, MemOperand(frame_pointer(), kStringStartMinusOne));

        // Initialize code pointer register
        __ mov(code_pointer(), Operand(masm_->CodeObject()));

        Label load_char_start_regexp, start_regexp;
        // Load newline if index is at start, previous character otherwise.
        __ CmpP(r3, Operand::Zero());
        __ bne(&load_char_start_regexp);
        __ mov(current_character(), Operand('\n'));
        __ b(&start_regexp);

        // Global regexp restarts matching here.
        __ bind(&load_char_start_regexp);
        // Load previous char as initial value of current character register.
        LoadCurrentCharacterUnchecked(-1, 1);
        __ bind(&start_regexp);

        // Initialize on-stack registers.
        if (num_saved_registers_ > 0) { // Always is, if generated from a regexp.
            // Fill saved registers with initial value = start offset - 1
            if (num_saved_registers_ > 8) {
                // One slot beyond address of register 0.
                __ lay(r3, MemOperand(frame_pointer(), kRegisterZero + kPointerSize));
                __ LoadImmP(r4, Operand(num_saved_registers_));
                Label init_loop;
                __ bind(&init_loop);
                __ StoreP(r1, MemOperand(r3, -kPointerSize));
                __ lay(r3, MemOperand(r3, -kPointerSize));
                __ BranchOnCount(r4, &init_loop);
            } else {
                for (int i = 0; i < num_saved_registers_; i++) {
                    __ StoreP(r1, register_location(i));
                }
            }
        }

        // Initialize backtrack stack pointer.
        __ LoadP(backtrack_stackpointer(),
            MemOperand(frame_pointer(), kStackHighEnd));

        __ b(&start_label_);

        // Exit code:
        if (success_label_.is_linked()) {
            // Save captures when successful.
            __ bind(&success_label_);
            if (num_saved_registers_ > 0) {
                // copy captures to output
                __ LoadP(r0, MemOperand(frame_pointer(), kInputStart));
                __ LoadP(r2, MemOperand(frame_pointer(), kRegisterOutput));
                __ LoadP(r4, MemOperand(frame_pointer(), kStartIndex));
                __ SubP(r0, end_of_input_address(), r0);
                // r0 is length of input in bytes.
                if (mode_ == UC16) {
                    __ ShiftRightP(r0, r0, Operand(1));
                }
                // r0 is length of input in characters.
                __ AddP(r0, r4);
                // r0 is length of string in characters.

                DCHECK_EQ(0, num_saved_registers_ % 2);
                // Always an even number of capture registers. This allows us to
                // unroll the loop once to add an operation between a load of a register
                // and the following use of that register.
                __ lay(r2, MemOperand(r2, num_saved_registers_ * kIntSize));
                for (int i = 0; i < num_saved_registers_;) {
                    if ((false) && i < num_saved_registers_ - 4) {
                        // TODO(john.yan): Can be optimized by SIMD instructions
                        __ LoadMultipleP(r3, r6, register_location(i + 3));
                        if (mode_ == UC16) {
                            __ ShiftRightArithP(r3, r3, Operand(1));
                            __ ShiftRightArithP(r4, r4, Operand(1));
                            __ ShiftRightArithP(r5, r5, Operand(1));
                            __ ShiftRightArithP(r6, r6, Operand(1));
                        }
                        __ AddP(r3, r0);
                        __ AddP(r4, r0);
                        __ AddP(r5, r0);
                        __ AddP(r6, r0);
                        __ StoreW(r3,
                            MemOperand(r2, -(num_saved_registers_ - i - 3) * kIntSize));
                        __ StoreW(r4,
                            MemOperand(r2, -(num_saved_registers_ - i - 2) * kIntSize));
                        __ StoreW(r5,
                            MemOperand(r2, -(num_saved_registers_ - i - 1) * kIntSize));
                        __ StoreW(r6, MemOperand(r2, -(num_saved_registers_ - i) * kIntSize));
                        i += 4;
                    } else {
                        __ LoadMultipleP(r3, r4, register_location(i + 1));
                        if (mode_ == UC16) {
                            __ ShiftRightArithP(r3, r3, Operand(1));
                            __ ShiftRightArithP(r4, r4, Operand(1));
                        }
                        __ AddP(r3, r0);
                        __ AddP(r4, r0);
                        __ StoreW(r3,
                            MemOperand(r2, -(num_saved_registers_ - i - 1) * kIntSize));
                        __ StoreW(r4, MemOperand(r2, -(num_saved_registers_ - i) * kIntSize));
                        i += 2;
                    }
                }
                if (global_with_zero_length_check()) {
                    // Keep capture start in r6 for the zero-length check later.
                    __ LoadP(r6, register_location(0));
                }
            }

            if (global()) {
                // Restart matching if the regular expression is flagged as global.
                __ LoadP(r2, MemOperand(frame_pointer(), kSuccessfulCaptures));
                __ LoadP(r3, MemOperand(frame_pointer(), kNumOutputRegisters));
                __ LoadP(r4, MemOperand(frame_pointer(), kRegisterOutput));
                // Increment success counter.
                __ AddP(r2, Operand(1));
                __ StoreP(r2, MemOperand(frame_pointer(), kSuccessfulCaptures));
                // Capture results have been stored, so the number of remaining global
                // output registers is reduced by the number of stored captures.
                __ SubP(r3, Operand(num_saved_registers_));
                // Check whether we have enough room for another set of capture results.
                __ CmpP(r3, Operand(num_saved_registers_));
                __ blt(&return_r2);

                __ StoreP(r3, MemOperand(frame_pointer(), kNumOutputRegisters));
                // Advance the location for output.
                __ AddP(r4, Operand(num_saved_registers_ * kIntSize));
                __ StoreP(r4, MemOperand(frame_pointer(), kRegisterOutput));

                // Prepare r2 to initialize registers with its value in the next run.
                __ LoadP(r2, MemOperand(frame_pointer(), kStringStartMinusOne));

                if (global_with_zero_length_check()) {
                    // Special case for zero-length matches.
                    // r6: capture start index
                    __ CmpP(current_input_offset(), r6);
                    // Not a zero-length match, restart.
                    __ bne(&load_char_start_regexp);
                    // Offset from the end is zero if we already reached the end.
                    __ CmpP(current_input_offset(), Operand::Zero());
                    __ beq(&exit_label_);
                    // Advance current position after a zero-length match.
                    Label advance;
                    __ bind(&advance);
                    __ AddP(current_input_offset(), Operand((mode_ == UC16) ? 2 : 1));
                    if (global_unicode())
                        CheckNotInSurrogatePair(0, &advance);
                }

                __ b(&load_char_start_regexp);
            } else {
                __ LoadImmP(r2, Operand(SUCCESS));
            }
        }

        // Exit and return r2
        __ bind(&exit_label_);
        if (global()) {
            __ LoadP(r2, MemOperand(frame_pointer(), kSuccessfulCaptures));
        }

        __ bind(&return_r2);
        // Skip sp past regexp registers and local variables..
        __ LoadRR(sp, frame_pointer());
        // Restore registers r6..r15.
        __ LoadMultipleP(r6, sp, MemOperand(sp, 6 * kPointerSize));

        __ b(r14);

        // Backtrack code (branch target for conditional backtracks).
        if (backtrack_label_.is_linked()) {
            __ bind(&backtrack_label_);
            Backtrack();
        }

        Label exit_with_exception;

        // Preempt-code
        if (check_preempt_label_.is_linked()) {
            SafeCallTarget(&check_preempt_label_);

            CallCheckStackGuardState(r2);
            __ CmpP(r2, Operand::Zero());
            // If returning non-zero, we should end execution with the given
            // result as return value.
            __ bne(&return_r2);

            // String might have moved: Reload end of string from frame.
            __ LoadP(end_of_input_address(), MemOperand(frame_pointer(), kInputEnd));
            SafeReturn();
        }

        // Backtrack stack overflow code.
        if (stack_overflow_label_.is_linked()) {
            SafeCallTarget(&stack_overflow_label_);
            // Reached if the backtrack-stack limit has been hit.

            // Call GrowStack(backtrack_stackpointer(), &stack_base)
            static const int num_arguments = 3;
            __ PrepareCallCFunction(num_arguments, r2);
            __ LoadRR(r2, backtrack_stackpointer());
            __ AddP(r3, frame_pointer(), Operand(kStackHighEnd));
            __ mov(r4, Operand(ExternalReference::isolate_address(isolate())));
            ExternalReference grow_stack = ExternalReference::re_grow_stack(isolate());
            __ CallCFunction(grow_stack, num_arguments);
            // If return nullptr, we have failed to grow the stack, and
            // must exit with a stack-overflow exception.
            __ CmpP(r2, Operand::Zero());
            __ beq(&exit_with_exception);
            // Otherwise use return value as new stack pointer.
            __ LoadRR(backtrack_stackpointer(), r2);
            // Restore saved registers and continue.
            SafeReturn();
        }

        if (exit_with_exception.is_linked()) {
            // If any of the code above needed to exit with an exception.
            __ bind(&exit_with_exception);
            // Exit with Result EXCEPTION(-1) to signal thrown exception.
            __ LoadImmP(r2, Operand(EXCEPTION));
            __ b(&return_r2);
        }

        CodeDesc code_desc;
        masm_->GetCode(isolate(), &code_desc);
        Handle<Code> code = isolate()->factory()->NewCode(code_desc, Code::REGEXP,
            masm_->CodeObject());
        PROFILE(masm_->isolate(),
            RegExpCodeCreateEvent(AbstractCode::cast(*code), *source));
        return Handle<HeapObject>::cast(code);
    }

    void RegExpMacroAssemblerS390::GoTo(Label* to) { BranchOrBacktrack(al, to); }

    void RegExpMacroAssemblerS390::IfRegisterGE(int reg, int comparand,
        Label* if_ge)
    {
        __ LoadP(r2, register_location(reg), r0);
        __ CmpP(r2, Operand(comparand));
        BranchOrBacktrack(ge, if_ge);
    }

    void RegExpMacroAssemblerS390::IfRegisterLT(int reg, int comparand,
        Label* if_lt)
    {
        __ LoadP(r2, register_location(reg), r0);
        __ CmpP(r2, Operand(comparand));
        BranchOrBacktrack(lt, if_lt);
    }

    void RegExpMacroAssemblerS390::IfRegisterEqPos(int reg, Label* if_eq)
    {
        __ LoadP(r2, register_location(reg), r0);
        __ CmpP(r2, current_input_offset());
        BranchOrBacktrack(eq, if_eq);
    }

    RegExpMacroAssembler::IrregexpImplementation
    RegExpMacroAssemblerS390::Implementation()
    {
        return kS390Implementation;
    }

    void RegExpMacroAssemblerS390::LoadCurrentCharacter(int cp_offset,
        Label* on_end_of_input,
        bool check_bounds,
        int characters)
    {
        DCHECK(cp_offset < (1 << 30)); // Be sane! (And ensure negation works)
        if (check_bounds) {
            if (cp_offset >= 0) {
                CheckPosition(cp_offset + characters - 1, on_end_of_input);
            } else {
                CheckPosition(cp_offset, on_end_of_input);
            }
        }
        LoadCurrentCharacterUnchecked(cp_offset, characters);
    }

    void RegExpMacroAssemblerS390::PopCurrentPosition()
    {
        Pop(current_input_offset());
    }

    void RegExpMacroAssemblerS390::PopRegister(int register_index)
    {
        Pop(r2);
        __ StoreP(r2, register_location(register_index));
    }

    void RegExpMacroAssemblerS390::PushBacktrack(Label* label)
    {
        if (label->is_bound()) {
            int target = label->pos();
            __ mov(r2, Operand(target + Code::kHeaderSize - kHeapObjectTag));
        } else {
            masm_->load_label_offset(r2, label);
        }
        Push(r2);
        CheckStackLimit();
    }

    void RegExpMacroAssemblerS390::PushCurrentPosition()
    {
        Push(current_input_offset());
    }

    void RegExpMacroAssemblerS390::PushRegister(int register_index,
        StackCheckFlag check_stack_limit)
    {
        __ LoadP(r2, register_location(register_index), r0);
        Push(r2);
        if (check_stack_limit)
            CheckStackLimit();
    }

    void RegExpMacroAssemblerS390::ReadCurrentPositionFromRegister(int reg)
    {
        __ LoadP(current_input_offset(), register_location(reg), r0);
    }

    void RegExpMacroAssemblerS390::ReadStackPointerFromRegister(int reg)
    {
        __ LoadP(backtrack_stackpointer(), register_location(reg), r0);
        __ LoadP(r2, MemOperand(frame_pointer(), kStackHighEnd));
        __ AddP(backtrack_stackpointer(), r2);
    }

    void RegExpMacroAssemblerS390::SetCurrentPositionFromEnd(int by)
    {
        Label after_position;
        __ CmpP(current_input_offset(), Operand(-by * char_size()));
        __ bge(&after_position);
        __ mov(current_input_offset(), Operand(-by * char_size()));
        // On RegExp code entry (where this operation is used), the character before
        // the current position is expected to be already loaded.
        // We have advanced the position, so it's safe to read backwards.
        LoadCurrentCharacterUnchecked(-1, 1);
        __ bind(&after_position);
    }

    void RegExpMacroAssemblerS390::SetRegister(int register_index, int to)
    {
        DCHECK(register_index >= num_saved_registers_); // Reserved for positions!
        __ mov(r2, Operand(to));
        __ StoreP(r2, register_location(register_index));
    }

    bool RegExpMacroAssemblerS390::Succeed()
    {
        __ b(&success_label_);
        return global();
    }

    void RegExpMacroAssemblerS390::WriteCurrentPositionToRegister(int reg,
        int cp_offset)
    {
        if (cp_offset == 0) {
            __ StoreP(current_input_offset(), register_location(reg));
        } else {
            __ AddP(r2, current_input_offset(), Operand(cp_offset * char_size()));
            __ StoreP(r2, register_location(reg));
        }
    }

    void RegExpMacroAssemblerS390::ClearRegisters(int reg_from, int reg_to)
    {
        DCHECK(reg_from <= reg_to);
        __ LoadP(r2, MemOperand(frame_pointer(), kStringStartMinusOne));
        for (int reg = reg_from; reg <= reg_to; reg++) {
            __ StoreP(r2, register_location(reg));
        }
    }

    void RegExpMacroAssemblerS390::WriteStackPointerToRegister(int reg)
    {
        __ LoadP(r3, MemOperand(frame_pointer(), kStackHighEnd));
        __ SubP(r2, backtrack_stackpointer(), r3);
        __ StoreP(r2, register_location(reg));
    }

    // Private methods:

    void RegExpMacroAssemblerS390::CallCheckStackGuardState(Register scratch)
    {
        DCHECK(!isolate()->IsGeneratingEmbeddedBuiltins());
        DCHECK(!masm_->options().isolate_independent_code);

        static constexpr int num_arguments = 3;
        __ PrepareCallCFunction(num_arguments, scratch);
        // RegExp code frame pointer.
        __ LoadRR(r4, frame_pointer());
        // Code of self.
        __ mov(r3, Operand(masm_->CodeObject()));
        // r2 becomes return address pointer.
        __ lay(r2, MemOperand(sp, kStackFrameRASlot * kPointerSize));
        ExternalReference stack_guard_check = ExternalReference::re_check_stack_guard_state(isolate());

        __ mov(ip, Operand(stack_guard_check));
        __ StoreReturnAddressAndCall(ip);

        if (base::OS::ActivationFrameAlignment() > kPointerSize) {
            __ LoadP(sp, MemOperand(sp, (kNumRequiredStackFrameSlots * kPointerSize)));
        } else {
            __ la(sp, MemOperand(sp, (kNumRequiredStackFrameSlots * kPointerSize)));
        }

        __ mov(code_pointer(), Operand(masm_->CodeObject()));
    }

    // Helper function for reading a value out of a stack frame.
    template <typename T>
    static T& frame_entry(Address re_frame, int frame_offset)
    {
        DCHECK_EQ(kPointerSize, sizeof(T));
#ifdef V8_TARGET_ARCH_S390X
        return reinterpret_cast<T&>(Memory<uint64_t>(re_frame + frame_offset));
#else
        return reinterpret_cast<T&>(Memory<uint32_t>(re_frame + frame_offset));
#endif
    }

    template <typename T>
    static T* frame_entry_address(Address re_frame, int frame_offset)
    {
        return reinterpret_cast<T*>(re_frame + frame_offset);
    }

    int RegExpMacroAssemblerS390::CheckStackGuardState(Address* return_address,
        Address raw_code,
        Address re_frame)
    {
        Code re_code = Code::cast(Object(raw_code));
        return NativeRegExpMacroAssembler::CheckStackGuardState(
            frame_entry<Isolate*>(re_frame, kIsolate),
            frame_entry<intptr_t>(re_frame, kStartIndex),
            frame_entry<intptr_t>(re_frame, kDirectCall) == 1, return_address,
            re_code, frame_entry_address<Address>(re_frame, kInputString),
            frame_entry_address<const byte*>(re_frame, kInputStart),
            frame_entry_address<const byte*>(re_frame, kInputEnd));
    }

    MemOperand RegExpMacroAssemblerS390::register_location(int register_index)
    {
        DCHECK(register_index < (1 << 30));
        if (num_registers_ <= register_index) {
            num_registers_ = register_index + 1;
        }
        return MemOperand(frame_pointer(),
            kRegisterZero - register_index * kPointerSize);
    }

    void RegExpMacroAssemblerS390::CheckPosition(int cp_offset,
        Label* on_outside_input)
    {
        if (cp_offset >= 0) {
            __ CmpP(current_input_offset(), Operand(-cp_offset * char_size()));
            BranchOrBacktrack(ge, on_outside_input);
        } else {
            __ LoadP(r3, MemOperand(frame_pointer(), kStringStartMinusOne));
            __ AddP(r2, current_input_offset(), Operand(cp_offset * char_size()));
            __ CmpP(r2, r3);
            BranchOrBacktrack(le, on_outside_input);
        }
    }

    void RegExpMacroAssemblerS390::BranchOrBacktrack(Condition condition, Label* to,
        CRegister cr)
    {
        if (condition == al) { // Unconditional.
            if (to == nullptr) {
                Backtrack();
                return;
            }
            __ b(to);
            return;
        }
        if (to == nullptr) {
            __ b(condition, &backtrack_label_);
            return;
        }
        __ b(condition, to);
    }

    void RegExpMacroAssemblerS390::SafeCall(Label* to, Condition cond,
        CRegister cr)
    {
        Label skip;
        __ b(NegateCondition(cond), &skip);
        __ b(r14, to);
        __ bind(&skip);
    }

    void RegExpMacroAssemblerS390::SafeReturn()
    {
        __ pop(r14);
        __ mov(ip, Operand(masm_->CodeObject()));
        __ AddP(r14, ip);
        __ Ret();
    }

    void RegExpMacroAssemblerS390::SafeCallTarget(Label* name)
    {
        __ bind(name);
        __ CleanseP(r14);
        __ LoadRR(r0, r14);
        __ mov(ip, Operand(masm_->CodeObject()));
        __ SubP(r0, r0, ip);
        __ push(r0);
    }

    void RegExpMacroAssemblerS390::Push(Register source)
    {
        DCHECK(source != backtrack_stackpointer());
        __ lay(backtrack_stackpointer(),
            MemOperand(backtrack_stackpointer(), -kPointerSize));
        __ StoreP(source, MemOperand(backtrack_stackpointer()));
    }

    void RegExpMacroAssemblerS390::Pop(Register target)
    {
        DCHECK(target != backtrack_stackpointer());
        __ LoadP(target, MemOperand(backtrack_stackpointer()));
        __ la(backtrack_stackpointer(),
            MemOperand(backtrack_stackpointer(), kPointerSize));
    }

    void RegExpMacroAssemblerS390::CheckPreemption()
    {
        // Check for preemption.
        ExternalReference stack_limit = ExternalReference::address_of_stack_limit(isolate());
        __ mov(r2, Operand(stack_limit));
        __ CmpLogicalP(sp, MemOperand(r2));
        SafeCall(&check_preempt_label_, le);
    }

    void RegExpMacroAssemblerS390::CheckStackLimit()
    {
        ExternalReference stack_limit = ExternalReference::address_of_regexp_stack_limit(isolate());
        __ mov(r2, Operand(stack_limit));
        __ CmpLogicalP(backtrack_stackpointer(), MemOperand(r2));
        SafeCall(&stack_overflow_label_, le);
    }

    void RegExpMacroAssemblerS390::CallCFunctionUsingStub(
        ExternalReference function, int num_arguments)
    {
        // Must pass all arguments in registers. The stub pushes on the stack.
        DCHECK_GE(8, num_arguments);
        __ mov(code_pointer(), Operand(function));
        Label ret;
        __ larl(r14, &ret);
        __ StoreP(r14, MemOperand(sp, kStackFrameRASlot * kPointerSize));
        __ b(code_pointer());
        __ bind(&ret);
        if (base::OS::ActivationFrameAlignment() > kPointerSize) {
            __ LoadP(sp, MemOperand(sp, (kNumRequiredStackFrameSlots * kPointerSize)));
        } else {
            __ la(sp, MemOperand(sp, (kNumRequiredStackFrameSlots * kPointerSize)));
        }
        __ mov(code_pointer(), Operand(masm_->CodeObject()));
    }

    void RegExpMacroAssemblerS390::LoadCurrentCharacterUnchecked(int cp_offset,
        int characters)
    {
        if (mode_ == LATIN1) {
            // using load reverse for big-endian platforms
            if (characters == 4) {
#if V8_TARGET_LITTLE_ENDIAN
                __ LoadlW(current_character(),
                    MemOperand(current_input_offset(), end_of_input_address(),
                        cp_offset * char_size()));
#else
                __ LoadLogicalReversedWordP(current_character(),
                    MemOperand(current_input_offset(), end_of_input_address(),
                        cp_offset * char_size()));
#endif
            } else if (characters == 2) {
#if V8_TARGET_LITTLE_ENDIAN
                __ LoadLogicalHalfWordP(current_character(),
                    MemOperand(current_input_offset(), end_of_input_address(),
                        cp_offset * char_size()));
#else
                __ LoadLogicalReversedHalfWordP(current_character(),
                    MemOperand(current_input_offset(), end_of_input_address(),
                        cp_offset * char_size()));
#endif
            } else {
                DCHECK_EQ(1, characters);
                __ LoadlB(current_character(),
                    MemOperand(current_input_offset(), end_of_input_address(),
                        cp_offset * char_size()));
            }
        } else {
            DCHECK(mode_ == UC16);
            if (characters == 2) {
                __ LoadlW(current_character(),
                    MemOperand(current_input_offset(), end_of_input_address(),
                        cp_offset * char_size()));
#if !V8_TARGET_LITTLE_ENDIAN
                // need to swap the order of the characters for big-endian platforms
                __ rll(current_character(), current_character(), Operand(16));
#endif
            } else {
                DCHECK_EQ(1, characters);
                __ LoadLogicalHalfWordP(
                    current_character(),
                    MemOperand(current_input_offset(), end_of_input_address(),
                        cp_offset * char_size()));
            }
        }
    }

#undef __

} // namespace internal
} // namespace v8

#endif // V8_TARGET_ARCH_S390
